High-temperature fan



Dec. 28, 1948. c. NYGREN HIGH TEMPERATU'RE FAN Filed A rii 28. 1945 5 Sheets-Sheet 1 I INVENTOR. dfl /lff'fl Dec? 1948- c. NYGREN 2,457,264

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Dec.2 8,1948. c. NYGR-EN 1 2,457,264

' HIGH TEMPERATURE FAN Filed April 28; 1945 5 Sheets-Skeet 4 Dec. 28,1948. c NYGREN m3 TEMPERATURE FAN Filed April 28, 1.945

. 5 Sheets-Sheet 5 II! III] Patented Dec. 28, 1948 HIGH-TEMPERATURE FAN Carl Nygren, Michigan City, llnd., assignor to Michiana Products Corporation, Michigan City, End, a corporation of Indiana Application April 28, 1945, Serial No. 590,753

10 Claims.

This invention relates to centrifugal fans or blowers for heat treating furnaces and the like, and the principal object of the invention is to provide a simple construction that can be readily manufactured from suitable heat and corrosion resisting alloys and will allow appropriate freedom of movement among the parts in expanding and contracting while maintaining dynamic balance of the whole in use.

Generally speaking, this is accomplished. by interlocking a plurality of separate, like blades in circular arrangement about a common axis of rotation so that they mutually sustain each other against individual outward movement as they expand and contract in use.

In the accompanying drawings, preferred forms of double inlet and single inlet fans are shown which should be considered merely as examples, for it is fully appreciated that the fundamentals of the invention are susceptible of a great many different embodiments too numerous to illustrate or attempt to describe.

Figs. 1 and 2 are diagrammatic views of a double inlet fan and its associated parts in one form of illustration Fig. 3 is a longitudinal sectional view through a double inlet fan and a hollow fan shaft taken on the line 33 of Fig. 2;

Fig. e is a side elevation of one of the twelve blades used in this particular fan;

Fig. 5 is an edge view of the fan shown in Fig.

Fig. 6 is a face view of one of the hub members used in this fan;

Fig. '7 is a horizontal section through the axis of Fig. 6;

Fig. 8 is a perspective view of one of the pins by which the several blades are interlocked to each other and to the hub members in this fan;

Fig. 9 is a perspective view of a spacer used between the two hub members in this fan as shown in Fig. 3;

Fig. 10 is a half section at right angles to the axis of the fan shown in Fig. 3 and a half end elevation of that fan;

Fig. 11 is a side elevation of one-half of one of the shroud rings, two of which are carried by the blades as shown in Figs. 8 and 10;

Fig. 12 is a view similar to Fig. 4 with the blade reversed or looking at Fig. 4 from the opposite side;

Fig. 13 is a longitudinal sectional view through a single inlet fan and hollow shaft taken on the line 33 of Fig 2;

Fig. 14 is a side elevation of one of the twelve blades used in this particular fan;

Fig. 15 is an edge elevation of Fig. 14;

Fig. 16 is a side elevation of another of the twelve blades used in this fan, six of them being as shown in this figure and six of the others being as shown in Fig. 14;

Fig. 17 is a half axial section through a fan similar to that shown in Fig. 3 but with a different kind of shroud construction, the several parts of which are individual to, integral with, and carried with the respective blades;

Fig. 18 is a partial section at right angles to the axis of Fig. 17 and a partial end elevation of the fan shown therein.

Fig. 19 is a side elevation of one of the twelve blades used in this particular fan;

Fig. 20 is an edge view of Fig. 19 looking fro the right; and

Fig. 21 is an end view ofthe blades shown in Fig. 19 looking from the top.

In Figs. 1 and 2, l0 indicates a conventional form of masonry installation for a fan or blower within which is a metal casing H for a double inlet fan l2 mounted on a hollow, water-cooled shaft l3 journaled in bearings i l and driven by a motor I5 through a V-belt drive Hi. The inlet side of a water cooling. unit is shown generally at ii, and the return side is shown generally at l8. Water cooling is ordinarily used in fan constructions for propelling high temperature fluids such as the gases recirculated in heat treating furnaces.

The detail of a double inlet fan is shown in Figs. 3-12, Sheets 2 and 3. The fan is composed of twelve blades I9. two circular shrouds 29, and two hub portions 2! assembled on the hollow shaft l3.

From the side views shown in Figs. 4 and 12, it will be seen that the fan blades in this instance are composed of a generally rectangular flat plate having the inner corners cut away at 22 to provide part of the inlet passages, and adjacent to these cut away corners there are legs 24 and 25 provided with feet 28 and 21 symmetrically arranged with respect to the legs 24 and 25 and the main body of the blade and having adjacent to each end holes or openings 28 and 29 (Fig. 5).

In this particular 24" fan, the legs M are 2%" from the center line of the blades, the legs 25 are 3%" from the center line of the blades,

and the feet 26 and 2. are thick measured along the axis of the fan. From this statement and a consideration of Figs. 5 and 12, it will be apparent that by reversing alternate blades in the series of twelve, they can be brought into the relation shown best in the right half of Fig. 10, in which the adjacent ends of the feet 26 of adjacent blades overlap (compare Figs. 3 and And thus the assembly in circular arrangement about the common axis of rotation may be secured togetherand-tothe hub members 2i by pins generally indicated at 39 (Figsfi3; 8, and 10)'. When thus assembled, the pins connect the circular arrangement of blades to form a chain; about the common axis of rotation in which all of the corresponding parts are equidistantirord that axis, and, as a naturalresult, if the-several. blades and pins are substantially the same. throughout the series there will be dynamic bal ance in which the whole can expand and contract as one, and each with properclearan'ces canex pand and contract individually while each blade is held against individual outward movement underthe action of centrifugal force. I o

In this particular designthe pins to are given three diameters for threelengths of theintermediate diameter 31 being-% and the two end diameters 32 being 34 The holes 23 and 7 .29 in the feet 26 and 2'! and the holes 33 in the flanges 34 of the hub members 29 are made to correspond with suitable clearances and tolerances; This arrangement not only interlocks the individual blades to each other in series, butalso to-the hub members and automatically makes the pins fast against-movement in any direction.-

The hub membersilare fixed tothe shaft is by three driving keys 35 spaced equidistant about the-axis of rotation and preferably fitted in-keyways to contact at thesidesonly; which a-I'e'made parallel; This" arrangement ofkeys provides proper driving connection between the shaft and the hub members while the shaftremains comparatively cool due-tothe circulation of water, and the hub members get relatively hot due'to contact with the recirculatedgases and the other members of the fan;

The-hub members are spaced'from' each other and held against binding-on the'assembled feet 2Ba'nd 21 bya'hollow; cylindrical spacer 36 telescoped'over the shaft 13." The lefthub'member 2 I in'Fig; 3 'is' seated against' an integral shoulder 31 on'the' shaft and the right hub member is made fast by a' collar '38'threaded on the-hollow shaft'set up against the hub member, and then backed ofi an amount corresponding to the calculatedor empirically determined-expansion. It islocked by lock washer 39 having afinger Ml hin a groove 4| in'shaft l3'an'd a'finger 42 bent over into a slot 43in a'lock'nut'd' l" also threaded on the shaft [3.

lzi-some service, the assembly thus far describedwill be suitable without anyshrouds.- In otliers', shro'udswillbe appropriate 'andin many instances considered indispensable; They" may be very" com/"eniently carried upon the blades" in sucha manner thatthey' float on the several blades-subject, in the main; to centrifugal force alo'ne, except in starting-andstopping' or in acceler'ation' or deceleration. In one way of accomplishing this, at or adjacent to each side edge 4 5 each blade is thickened and provided with grooves fl wherebyateachside of each groove there appearribs fland' tt', the ribs 4'! being relatively short arid the'ribs being relatively long approXima-tely as long at the edges if: as the-shrouds are wide;

Each-shroud "251553. "ring, here :shown as -pro.- vided with outwardly opening slots 49, twelve in number, to receive the side edges of the several blades as the adjacent portions of the slots are received between the ribs ll and Q8. The shrouds are of uniform thickness to about the depth or" the slots 49, and from there inwardly they are gradually thickener as indicated at 553 to provide additional strength for resisting. the bursting tendenciesiof centrifugal force onthe shrouds as a Whole.

With the shrouds thus mounted on the outer portions of the blades at their side edges, the shreuds-an'd-those portions of the blades are free to expand and-contract independently, and yet the twelve supports-for the circular shrouds adiacent to'th'e outer edge of the wheel serve to center the shrouds very accurately without putting any bending strains on the blades.

Asan empirical rule, the slots t9 should not ordinarily be deeper than one-third of the radial depth of theshrouds, and they need not in fact be that depth for ordinary purposes;

When forany reason, suchas the corrosive atmosphere and the hightemperatures, it becomes necessaryto use alloys in the blades that are likely to crack outwardly of the pins 30, a safeguard against the broken portion of a blade flying out'under centrifugal force and doing damage to the assembly as a whole maybe obtained by-providing the slots in the shrouds opening-from theinner side, or; better still, the interlocking connection may. be made by special projections extending inwardly from the inner periphery of the shrouds and cooperating with suitable projections on the blades, an illustration of which will be found in a copending application, Serial No. 590,754 filedApril28', 1945, now PatentNo.2,428,765,;issued October 7, 1947. v

Figs;-13-16' (Sheet 4) show a single inlet'ian corresponding in all other respects-to the construction describedinconnection with Figs, 3 12 (Sheets 2 and 3) with the followingexceptions: Six of theblades' H9 correspondtothe form shown in Fig. 14 and the other sixto the form shown in Fig. 16 so as to provide for the overlapping-and-interlocking of the testes described in connection with the double inlet fanand-also to provide for the closure atthe side opposite-the sing-leinlet, which is formed-by the shroudsim (Fig. 13). Beyond theseexceptions, it is deemed sufficient tomerely add thecorrespcnding reference numerals to Figs. 13-16.

Figs.-17'2l (Sheet 5) show a tan construction corresponding to that shown in Figs. 3-12 (Sheets 2--and 3), except asto-the shrouds. In this-instance, each blade 2l9 has a shroud section '88 at one side and a shroudsection iii at the opposite side whereby the'blades are given asort of H formatian cross-s ction at th ut r p tion, 8 illappear-bes n Fie- The several shroud portio s 60 have machined faces 62 adapted to be received within the flanges 63* forming; forks t the-free ed es of the shroud portions 51. The assembly ofthese several shroud portions 69 and Bi around the circular arrangement completes the shrouds and makes them'in-efiect complete circles carried by the several blades with freedom {for expansion radially and-circumierentially and-having their weight so evenly distributed equidistantly with respect-to the axis of rotation as to give dynamic balanceto the whc l-. Outside'ci this e c pt n the co struction-issubstantially the-same as described in connection with Figs. 3-12 (Sheets-g and 3)".

Further details of this construction are given in copending application Ser. No. 594,750, filed May 19, 1945 According to the preferred practice, the hub portions, blades, shrouds, etc., are formed of a suitable alloy and machined to make all the corresponding parts substantially identical. After machining, the parts are annealed at a temperature above the highest to be expected in service in order to remove internal strains that might be released in service and throw the fan out of balance. By weighing the blades and a slight amount of fitting, the assembly can be readily given dynamic balance and the construction described will insure the maintenance of that balance in service as well as the necessary strength for a long period of service.

The choice of the alloy to be used will be effected by the temperature to be endured and the corrosive nature of the atmosphere, or the lack of any corrosiveness in the atmosphere. Metallurgists will understand that some alloys having a high resistance to corrosion do not have high strength at high temperatures and some sort of compromise will occasionally have to be ade- These things will affect some of the clearances and other features of design and construction, but, as an example, the pins 30 should have a push fit-for example, not more than .002 clearance in the hole. The blades and shrouds shown in Figs. 3-12 should fit with tolerances of plus .002" minus .000". The hub members should fit the shaft with tolerances of plus .001" minus .000".

In the preferred construction, the pins 30 in the holes 28 and 29 in the feet 25 and 27 take all of the radial stress due to centrifugal forces, and the driving stress is taken by that portion of the pins entering the holes in the hub members. Of course, some engineers will prefer to vary this, and indeed some will wish to effect a more positive driving and stabilizing relation between the hub members and the blades by fitting the feet and, in some instances, the inner portions of the blades into slots in the hub members corresponding to the arrangement shown in copending application Ser. No. 589,565, filed April 21, 1945 now Patent No. 2,385,838, issued October 2, 1945. But, in the interest of brevity, specific illustration and description of those things have been omitted.

I claim:

1. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with the inner portions converging inwardly toward said axis and the outer portions diverg ing outwardly from said axis, hub members overlapping the assembled inner end portions of the blades, and means between each pair of adjacent blades for making said inner end portions of the blades fast to each other and t0 the hub portions to hold them against individual bodily movement outwardly due to centrifugal force and rotary movement relative to the hub portions,

2. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with the inner portions converging inwardly toward said axis and the outer portions diverging outwardly from said axis, hub members overlapping the assembled inner end portions of the blades, and means between each pair of adjacent blades for interlocking said inner end portions of the blades fast to each other and to the hub portions to hold them against individual bodily movement outwardly due to centrifugal force and rotary movement relative to the hub portions.

3. In a centrifugal fan, a plurality of blades in circular arrangement about a. common axis of rotation with their outer portions diverging out wardly from said axis and their inner portions converging toward said axis and overlapping in series about it, hub portions at either side thereof, and means between each pair of adjacent blades for making the overlapping inner end portions of the blades fast to each other and to the hub portions to hold them against individual bodily movement outwardly due to centrifugal force and rotary movement relative to the hub portions.

4. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their outer portions diverging outwardly from said axis and their inner portions converging toward said axis and overlapping in series about it, hub portions at either side thereof, and means equidistant from the axis and between each pair of adjacent blades for making the overlapping inner end portions of the blades fast to each other and to the hub portions to hold them against individual bodily movement outwardly due to centrifugal force and rotary movement relative to the hub portions.

5. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their outer portions diverging outwardly from said axis and their inner portions converging toward said axis and overlapping in series about it, hub portions at either side there of, and pins between each pair of adjacent blades making the overlapping inner end portions of the blades fast to each other and to the hub portions to hold them against individual bodily movement outwardly due to centrifugal force and rotary movement relative to the hub portions.

6. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their outer portions diverging outwardly from said axis and their inner portions converging toward said axis and overlapping in series about it, and pins between each pair of adjacent blades fastening together said overlapping inner end portions of the blades in a circuit about the axis to hold the blades against individual bodily movement outwardly due to centrifugal force.

7. A fan blade comprising a generally rectangular flat body having its lower corners cut away, legs extending from the inner edge of the body adj acent to the cutaway corners, and a foot on each leg symmetrical with respect to it and extending transversely to it.

8. A fan blade comprising a generally rectangular fiat body having legs extending inwardly from its inner end portion and located unequal distances on opposite sides of the center line of the body, and feet projecting laterally from each side of each leg, whereby a plurality of blades are adapted to be alternately reversed about an axis of rotation with adjacent feet overlapping for connection together by means extending through said feet.

9. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with the inner portions converging inwardly toward said axis and the outer portions diverging outwardly from said axis, a pair of legs extending inwardly from the inner end portion of each blade with the legs of each pair located unequal distances on opposite sides of the center line of each blade, feet projecting laterally from each side of each leg, adjacent blades being reversed whereby the feet of each blade overlap the feet of the adjacent blade, hub members overlapping the assembled inner end portions of: the. b ades, nd means, extending thro gh ach pairof overlapping feet and through the hub members for holding the blades together and to the. hub members against; individual bodily movement outwardly due to centrifugal force and a ainst rotary movement relative to. the hub mem bars. 1 l

10, In a centrifugal; fan, a plurality of blades in circular arrangement, about a common axis of rotation with the inner portions converging in? wardly-toward said axis and the outer portions diverging outward y from said axis, a p r of latorally projeoting feet. iormed on the radially inmen portion of each blade on each opposite side of the radial center linev of the blade with one pair. of feet axially farther from said center line thanthe other pair whereby the feet of each blade in the circular arrangement overlap the REFERENCES CITED The following references are of record in the fiie of this patent:

UNITED STATES PATENTS Number Name Date 1,191,040 Sherwood July 11, 1916 2,130,145 McKee Sept. 13, 1938 

